Metal punch

ABSTRACT

A metal punch for use by an electrician to punch holes in boxes, panels and cabinets comprising a pair of spaced, coplanar, elongated rectangular jaw bars interconnected at one of their ends such that they may be pivoted from a parallel position to positions in which their free ends diverge; a screw received through a threaded bore running perpendicularly through the free end of one of the jaw bars; a conventional, presently available punch element mounted on the end of the shank of the screw such that it moves axially with the shank without rotation; a die attached to the end of the other jaw bar with its bore facing and aligned with the punch element when the jaw bars are substantially parallel; and a collar which slides over the jaw bars and restrains them in a substantially parallel position and keeps them from twisting when the punch is operated.

United States Patent [1 1 Hughes, Jr.

[451 Apr. 2, 1974 METAL PUNCH [76] Inventor: Carter S. Hughes, Jr., P.0 Box 743,

Fallon, Nev. 89406 I [22] Filed: Dec. 22, 1972 [21] Appl. No.: 317,527

Primary Examiner-Othell M. Simpson Assistant ExaminerMarc R. Davidson [57] ABSTRACT A metal punch for use by an electrician to punch holes in boxes, panels and cabinets comprising a pair of spaced, coplanar, elongated rectangular jaw bars interconnected at one of their ends such that they may be pivoted from a parallel position to positions in which their free ends diverge; a screw received through a threaded bore running perpendicularly through the free end of one of the jaw bars; a conventional, presently available punch element mounted on the end of the shank of the screw such that it moves axially with theshank without rotation; a die attached to the end of the other jaw bar with its bore facing and aligned with the punch element when the jaw bars are substantially parallel; and a collar which slides over the jaw bars and restrains them in a substantially parallel position and keeps them from twisting when the punch is operated.

7 Claims, 4 Drawing Figures METAL PUNCH BACKGROUND OF THE INVENTION l. Fieldof the Invention This invention relates to a new metal punch. More specifically it relates to a metal punch for use by electricians in punching holes in junction boxes and which is adapted to use conventional punch and die elements.

2. Description of the Prior Art Electricians regularly use metal punches for enlarging knockouts and punch holes for conduit in metal boxes, panels and cabinets. The punch most prevalently used by the average electrician is of the type described in U. S. Pat. No. 1,817,223. (commercially available from Greenlee Tool Co.). The embodiment presently sold commercially is a punch set consisting of a three-eighths inch and three-fourths inch screw and four pairs of punch elements and die cups ranging in quarter inch sizes between one-half inch and 1% inches, inclusive. The three-eighths inch screw is used with the one-half inch die-punch and the three-fourths inch screw is used with the other die-punch pairs in the set. The set is used as follows: a hole is first drilled in the box, cabinet or panel of sufficient diameter to accomodate the screw of the set. The die is then placed on one side of the member to be punched over the drilled hole and the shank is run through the die and the hole. The punch is then threaded onto the screw until it is firmly against the other side of the member. The screw is then tightened further by hand thus forcing the punch through the member into the die.

SUMMARY OF THE INVENTION The present invention is a punch which is fairly compact and may be operated by a single person, which requires no drilling of holes to use and which is adapted to employ the die-punch pairs presently in use. Because no drilling is required, holes may be punched much faster than with the punch sets described above.

This novel punch comprises: a frame having a pair of spaced, elongated coplanar jaw bars interconnected at one of their ends, at least one of the jaw bars being pivotally hinged whereby it may be moved from a position parallel to the other bar to positions in which its free end diverges from the free end of the other bar; a screw threadedly received perpendicularly through the free end of one of the jaws; a punch mounted on the end of the shank of the screw such that it follows the axial movement of the shank without following the rotation thereof; a die removably attached to the free end of the other jaw with its bore facing and aligned with the punch when the jaw bars are substantially parallel and a collar or clamp which fits around the jaw bars thereby preventing them from opening or twisting during the punching operation.

As indicated above this punch is especially adapted to employ the above described commercial punch sets. The punch-die pairs of the set may be used as is without modification. However a screw (preferably the threefourths inch one) of the set must be modified such that the punch mounted on its end is driven axially but not rotationally by the turning of the'screw. As described hereinafter such modification may be accomplished by drilling an axial hole in the shank of the screw and using an adapter which has a shaft which slides into the axial hole and a threaded head on which the punch is received.

Punching holes with this punch is a much simpler operation than punching holes with the above described prior art punch set. The desired die is first attached to one of the jaw bars andthe screw is threaded through a bore in the other jaw bar. The jaw bars are then opened by pivoting one (or both as the case may be) of them and the adapter-punch combination is slid into the axial hole in the screw and held in place by hand. The jaws are then closed parallel over the metal sheet to be punched and the collar is slid over the interconnected ends of the jaw bars. The screw is then turned to drive the punch through the metal sheet and into the die bore. After the punching is completed the collar is slid off, the jaws are opened and the punched out piece of metal is extracted from the die. In comparison with the prior art, no drilling is required in order to use the invention punch. Furtherq it may be disassembled and reset much quicker than the prior art punch set-making its use in repetitive punching much more advantageous.

Accordingly a principal object of this invention is to provide a fairly compact punch which may be handled by one man and which is adapted to employ presently used punch-die sets.

A further object is to provide a punch which does not require any pre-drilling of holes and which may be easily disassembled and reset for repetitive punching.

These objects and others will be apparent from the accompanying drawings and the following description of the preferred embodiment of this punch.

BRIEF DESCRIPTION OF'DRAWINGS FIG. 1 is a perspective view of the preferred embodiment of the invention;

FIG. 2 is an enlarged, vertical, sectional view taken along line 2--2 of FIG. I;

FIG. 3 is a section view taken along line 33 of FIG. 2; and

FIG. 4 is a partial, vertical, cross-section showing the adaption of the punch for using different punch and die elements.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the basic elements of the invention punch: a frame generally designated 1 comprising a pair of coplanar, elongated, spaced, rectangular jaw bars 2, 3 interconnected at one of their ends by spaced flat plates 4, 5; a collar 6 which is adapted to slide over jaw bars 2,3 at their interconnected ends; a threaded bolt 7 received through the unconnected end of jaw bar 2; a punch element 8 mounted on the end of the shank of bolt 7; and a die element 9 attached to inner side of jaw bar 3.

As illustrated in FIG. 1 in phantom the narrowed end 10 of jaw bar 2 is pivotally hinged between interconnecting plates 4, 5 on pin 14; whereas the interconnected end of bar 3 is mounted between plates 4, 5 in a fixed position by screws l5, 16. When jaw bar 2 is pivoted to a position essentially parallel to jaw bar 3 shoulders 17 forming the transition between narrowed end 10 and the full perimeter of bar 2 fit snugly against the corresponding corner (not shown) of plate are rounded to permit shoulders 17 to clear plates 4, 5 when bar 2 is pivoted away from bar 3 (upwardly in FIG. 1). In other words bar 2 is mounted so that it may be pivoted from a position in which it is parallel to bar 3 to positions in which the free ends of bars 2, 3 diverge. Such pivoting allows the punch jaws to be opened to permit easy access over deep lips on large junction boxes. It also provides easy disengagement of the punch from the sheet in which the hole is being punched and facilitates extracting the disc of punched out metal from the die element.

The spacing between bars 2, 3 when they are substantially parallel is not critical but is important for a practical reason. As previously indicated the punch of the invention is designed primarily to use the punch and die elements of conventional electricians knock-out punches, such as those available from Greenlee Tool Company. Such elements may be used to punch out sheet metal up to one-eighth inch thick but may be damaged if used to punch out thicker sheeting. Accordingly the spacing between bars 2, 3 when they are substantially parallel is such that the clearance between the cutting edge of the punch element 8 and the die element 9 is just slightly greater than one-eighth inch. With such spacing the elements cannot be used on thicker sheeting and be damaged.

Collar 6 has a central rectangular hole 21 whose perimeter is slightly larger than the rectangular perimeter ofthe connected end of frame 1 when bars 2, 3 are substantially parallel. As shown in FIGS. 2 and 3 collar 6 is adapted to be snugly slid over connected end of frame 1, thereby locking bars 2, 3 in a substantially parallel position. This ensures that the punch element and die element will merge in proper alignment. Collar 6 must be of sufficient area and strength to withstand the bearing pressure and tension created during the punching operation without permitting jaw bar 2, 3 to separate or twist.

As seen in FIG. 2 bolt 7 is the driving member which drives the punch element 8 down into the bore of the die element 9. The shank 22 of bolt 7 is threaded and is received through a threaded bore 23 running perpendicularly through bar 2 near the free end thereof. Shank 22 has a central axial hole 24 drilled in it which receives an adapter, generally designated 25. Adapter 25 comprises a thin, cylindrical shaft 26 which is slidably received within hole 24 and an externally threaded, integral head 27 which is threadedly received into the threaded bore 28 of punch element 8 (conventional knock-out punches have either a three-eighths inch or three-fourths inch threaded bore).

When bolt 7 is turned (by hand or with a wrench 30 shown in phantom in FIG. 2) so that its shank 22 is driven into the space between bars 2, 3 (downward in the drawings) there is essentially no rotational movement of punch element 27 because the end ofshank 22, the non-cutting end of punch element 8 in contact therewith and the surfaces of bore 24 and shaft 26 are all fairly smooth. Accordingly, such turning transmits only axial movement to punch element 8.

The die element 9 is removably attached to the top side of bar 3 with its opening 29 axially aligned with and facing the cutting edge of punch element 8. The attachment is effected by flat washer 33 and bolt 34 which is received through hole 35 in the bottom of die element 9 and within threaded bore 36 which runs perpendicularly through bar 3 near the free end thereof. Hole 35 is fitted with a sleeve 37 to prevent die element 9 from slipping.

FIG. 4 shows a variation of adapter 25 which is used with smaller punch element 32 (normally seven-eighths inch in diameter and smaller with a three-eighths inch bore). The smaller sets require an adapter generally designated 38 which includes a smaller diameter head 39, a shaft 40 identical in structure and function to shaft 26 and a cylindrical extension section 41 intermediate head 39 and shaft 40. Extension section 41 is required because smaller die element 42 is shallower than element 9 and the proper spacing (approximately oneeighth inch) must be maintained between the punch and die elements. Accordingly, the thickness of section 41 is the same as the difference between the depth of element 9 and the depth of element 42. As shown in FIG. 4 the diameter of section 41 must be at least about as great as the diameter of shank 22 so that it provides an adequate bearing surface.

In operation the desired die element is attached to bar 3. The desired punch element-adaptor combination is put together and the shaft of the former is slid into hole 24 of bolt 7 and the combination held in place with one hand. Jaw bars 2, 3 are then pulled apart, if necessary, and the sheet metal 43 to be punched is inserted between the jaw bars (FIGS. 2, 4). Jaw bars 2, 3 are then closed to a parallel position and collar 6 is slid over the connected end of frame 1 (preferably to at least about the midpoint thereof). Bolt 7 is then turned by hand or with a wrench such that punch element 8 is driven downward, punching through sheet metal 43 into opening 29 of die element 9. After the hole is punched, collar 6 is removed, jaw bar 2 is pivoted open and the punched out piece of sheet metal is extracted from the die element.

Various modifications of the preferred embodiment described above may be made without making any material changes in its structure or mode of operation. For instance, both jaw bars could be made pivotal rather than merely one or various clamp mechanisms might be used in place of collar 6. Also, the adapters might be built integrally into bolt 7 rather than being removable therefrom. These and other modifications will be obvious to one or ordinary mechanical skill and are intended to be within the scope of the following claims.

I claim:

1. A metal punch comprising:

a. a pair of elongated, coplanar, spaced jaw bars interconnected at one of their ends, at least one of said jaw bars being pivotal from a position parallel to the other bar to positions in which its unconnected end diverges from the unconnected end of the other bar;

b. a screw threadedly received perpendicularly through the unconnected end of one of said jaw bars with its shank extending into the space between the jaw bars;

c. a punch element mounted on the end of said shank such that it moves axially with the shank without substantial rotation;

d. a die element attached to the unconnected end of the other one of said jaw bars, said die element having a bore facing and aligned with the punch element when the jaw bars are substantially parallel for slidably receiving the punch element; and

e. means for restraining said jaw bars in a substantially parallel position without twisting during the punching operation.

2. A metal punch according to claim 1 wherein:

f. said means for restraining said jaw bars is a collar for sliding over the interconnected ends of the jaw bars when they are substantially parallel.

3. A metal punch according to claim 1 wherein:

f. only one of said jaw bars is pivotal; and

g. the screw is received through the one of said jaw bars that is pivotal.

4. A metal punch according to claim 1 wherein:

f. the screw has an axial hole; and including g. an adapter comprising a shaft for sliding into said axial hole and a head forreceiving the punch element.

5. A metal punch according to claim 1 wherein:

f. the maximum spacing between the die element and the punch element when the jaw bars are substantially parallel is approximately one-eighth inch.

6. A metal punch comprising:

a. a pair of elongated, coplanar, spaced, rectangular jaw bars;

b. a member interconnecting said jaw bars at one of their ends, one of said jaw bars being pivotally hinged to said member whereby it may be pivoted from a position substantially parallel to the other jaw bar to positions in which the other of their ends diverge;

c. a threaded bore extending perpendicularly through the pivotally hinged jaw bar near its unconnected end;

(1. a screw received through said threaded hole with its shank extending into the space between the jaw bars;

e. an axial, cylindrical hole in said shank;

f. an adapter comprising a cylindrical shaft which is slidably received within said axial, cylindrical hole and is rotatable therein and an externally threaded head;

g. a punch element having a threaded bore by which it is received onto the externally threaded head of the adapter;

h. a die element removably attached to the other of the jaw bars, said die element having a bore which faces and aligns-with the punch element when the jaw bars are substantially parallel; and

. a collar for sliding over the interconnected ends of the jaw bars when the jaw bars are substantially parallel, said collar restraining the jaw bars in a substantially parallel position and preventing them from twisting when the punch is operated.

7. A metal punch according to claim 6 wherein:

j. the maximum spacing between the die element and the punch element when the jaw bars are substantially parallel is approximately one-eighth inch. 

1. A metal punch comprising: a. a pair of elongated, coplanar, spaced jaw bars interconnected at one of their ends, at least one of said jaw bars being pivotal from a position parallel to the other bar to positions in which its unconnected end diverges from the unconnected end of the other bar; b. a screw threadedly received perpendicularly through the unconnected end of one of said jaw bars with its shank extending into the space between the jaw bars; c. a punch element mounted on the end of said shank such that it moves axially with the shank without substantial rotation; d. a die element attached to the unconnected end of the other one of said jaw bars, said die element having a bore facing and aligned with the punch element when the jaw bars are substantially parallel for slidably receiving the punch element; and e. means for restraining said jaw bars in a substantially parallel position without twisting during the punching operation.
 2. A metal punch according to claim 1 wherein: f. said means for restraining said jaw bars is a collar for sliding over the interconnected ends of the jaw bars when they are substantially parallel.
 3. A metal punch according to claim 1 wherein: f. only one of said jaw bars is pivotal; and g. the screw is received through the one of said jaw bars that is pivotal.
 4. A metal punch according to claim 1 wherein: f. the screw has an axial hole; and including g. an adapter comprising a shaft for sliding into said axial hole and a head for receiving the punch element.
 5. A metal punch according to claim 1 wherein: f. the maximum spacing between the die element and the punch element when the jaw bars are substantially parallel is approximately one-eighth inch.
 6. A metal punch comprising: a. a pair of elongated, coplanar, spaced, rectangular jaw bars; b. a member interconnecting said jaw bars at one of their ends, one of said jaw bars being pivotally hinged to said member whereby it may be pivoted from a position substantially parallel to the other jaw bar to positions in which the other of their ends diverge; c. a threaded bore extending perpendicularly through the pivotally hinged jaw bar near its unconnected end; d. a screw received through said threaded hole with its shank extending into the space between the jaw bars; e. an axial, cylindrical hole in said shank; F. an adapter comprising a cylindrical shaft which is slidably received within said axial, cylindrical hole and is rotatable therein and an externally threaded head; g. a punch element having a threaded bore by which it is received onto the externally threaded head of the adapter; h. a die element removably attached to the other of the jaw bars, said die element having a bore which faces and aligns with the punch element when the jaw bars are substantially parallel; and i. a collar for sliding over the interconnected ends of the jaw bars when the jaw bars are substantially parallel, said collar restraining the jaw bars in a substantially parallel position and preventing them from twisting when the punch is operated.
 7. A metal punch according to claim 6 wherein: j. the maximum spacing between the die element and the punch element when the jaw bars are substantially parallel is approximately one-eighth inch. 